The speed box I do not think it has a problem, look you have the next test, you have walk the vehicle and disconnect the Relay actuator, this actuator goes in the admission body where the thick hose that breaks of the filter, is bass or next to the TPC, is enters, well when the vehicle will fail to fail if it is the same with problems, hit it with a screwdriver and the revolution will vary. Surely that is the problem, now if you want to see if you have a false air input as my friend Megabeat_1 says, disconnects the flow and the vehicle has to stop if you do not do it you have a false air input problem, the release would also be to stop, when disconnected, you have the prebuena is easy.